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Old 07-03-16, 09:17 AM   #1
SentinelAeon
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Default Cooling down mansard apartment

Hi,

I have a few questions about cooling my small mansard apartment without AC. As you can see on an image i posted, i have 2 windows on same side, i have kitchen exhaust (hood) that i have been using to remove hot air, and there is another exhaust in the bathroom where i could mount a small 140mm (4,7 inch) fan to draw air out.


because this is my first post i cannot post images, here is the link:

i65.tinypic.com/8vxi7n.jpg


1) I have 2 quite big table fans that i put on windows, what would be the best setup for them, both blowing in, 1 blowing in, 1 out, etc. ?

2) I know that it takes a lot of cold air to cool down that big mass of bricks in walls but still. The apartment heats up so fast, even on first hot day it becomes hot fast. And then when it is cold outside it takes hours and hours to cool it down and as soon as i stop the fans and close the windows it gets hot again. Anything i can do to cool down more efficiently ?

3) In my country there is usualy about 5 hot days and then it will get cool for a few days and then hot again. I was wondering, if i were to use a lot of water (in bottles), and make sure i cool them down during the cold period, would that help in keeping my apartment cool for a while longer ? It would probably take a lot of water in bottles of barrels but would it help ?

4) I have a nice small water pump and 2 big window shelfs that are about 70x70 cm each (27.5 x 27.5 inch) and are covered in some kind of metal sheet. Since fans are doing a bad job at cooling the apartment, i was wondering, what if i were to use water to cool down apartment ? I can pour water on window shelf and then pump this water into an inside barrel full of water and create a loop. How would that work ?

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Old 07-03-16, 11:37 AM   #2
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Take a look at Delta fans. They are inverter drive and have a very high power density. One would work nicely for the bathroom exhaust.
Here's one for under $15. You'll also need a 12V power supply capable of supplying at least 4A, of which an old PC PSU works nicely. And a simple 555 circuit if you want to run it at less than full power at some times.
https://smile.amazon.com/Original-De.../dp/B00L5XEKOS

For the two big windows, most likely the most efficient configuration would be a box fan blowing in on one window and just leave the other window open.
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Old 07-03-16, 11:56 AM   #3
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Thank you for your answer !

There is another hole in the bathroom with water pipes inside, where i can open/close water. But what is interesting is that air is flowing into this hole meaning out of bathroom as long as my windows are opened. I was thinking of using some of the fans i already have at home, i have some heavy duty DC San Ace 12V 0.52A fans:

ebay.com/itm/Sanyo-Denki-109R1212H1011-Brushless-DC-San-Ace-Fan-12V-0-52A-120x120x38mm-/111606671624

They have only half the CFM of delta fan but i can use 2 of them and it doesn't cost me anything, and i can use a laptop power suply to power them, maybe use potenciometer/resistors to make it 12V.

ps: just a funny observation with my DC San Ace fan ... i tried running them on 12V AC for a long time and it worked just fine, no overheating or anything. I do know that when connecting some other smaller 12V fan to the same 12V AC it was overheating and u could smell it burning.
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Old 07-03-16, 01:44 PM   #4
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A few 12V DC fans are universal in that they also run on AC but most are not.

Since you already have the fans, give them a try. Sanyo (San Ace) has traditionally used analog inverters (not sure if it has changed since then) while Delta started using the far superior DSP inverter since 2009 or so. Therefore, it's probably worth upgrading if the idea works.
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Old 07-03-16, 08:24 PM   #5
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Do you own the apartment or are you renting?
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Old 07-04-16, 08:19 AM   #6
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Yesterday i tried setting 2 vents on that hole i mentioned, basicly covering the hole and putting 2 vents blowing in. Those vents are quite strong, they actualy close the bathroom door, if i don't wedge them.

I do hope this will make a difference. To be honest, till now with only window fans it really only made a difference as long as they were on, the moment i turned the fans off, apartment started heating up again. I hope that is because i had no exhaust fans and cold air only penetrated part of the apartment. The other explanation is that no amount of airflow will help because building mass is simply to big to be affected by air, i hope that is not the case.

I am renting it.
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Old 07-05-16, 05:39 PM   #7
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Stop the energy before it ever even enters your living space. If you have any way of doing so, affixing shades OUTSIDE the windows will go a long way to helping you. It's not everything of course, but it's not nothing either.

I live in East Tennessee, US, and it's hot and humid here. During the day I keep everything closed up as much as possible. When it cools off at night is when I open all the windows and put fans in - one blowing in, one blowing out. Generally if the temperatures go below about 18.5C, I'll do the open windows thing. Anything warmer than that and the fans don't help much - unless you're unfortunate enough to have no air conditioning, in which case do whatever you can.
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Old 07-06-16, 04:58 PM   #8
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The general rule of thumb is at least double the exhaust size hole compare to the hole the fan is blowing into. At least that is modern fire fighting rule of thumb.

Is the any way to put a screen in a doorway and leave the door open? That will help a lot. They make these new cool magnetic screens that auto close behind you.
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Old 07-06-16, 05:51 PM   #9
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Fans seem to be doing fine so far, i am waiting for a heat wave to really test the difference. Fan are working all day, when i go to sleep i put them on lower rpm with resistor, in the evening i open windows, during the day i leave a small gap in the doors. Another thing i did was put 2 wet towels over the windows so that during the day when that area heats, the dry air in that area will help water evaporate and cool the area. And then that air is pulled outside anyway.

Since water is quite cheap in my country, i was thinking of evaporative cooling. I did a small scale cooler last year and tested the temperatures and it worked, but it was sadly to small for anything else then blowing cold air into me. But now that i have those fast fans pulling air out ... couldnt i do a bit bigger scale ? I know air will get moist but it will soon exist the apartment and get replaced by less humid air ? I was also thinking of putting 2 small water sprays on my big window shelfs on the outside, something that would spray water very slowly, i tried using my small water pipe but sadly it wasnt strong enough to produce spray when connected to small plant sprayer.
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Old 07-07-16, 05:21 AM   #10
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Quote:
Originally Posted by SentinelAeon View Post
Fans seem to be doing fine so far, i am waiting for a heat wave to really test the difference. Fan are working all day, when i go to sleep i put them on lower rpm with resistor, in the evening i open windows, during the day i leave a small gap in the doors. Another thing i did was put 2 wet towels over the windows so that during the day when that area heats, the dry air in that area will help water evaporate and cool the area. And then that air is pulled outside anyway.
Once you add in a way to create cooling below ambient temps then you really need a way to keep heat out of the enclosure. The issue isn't necessarily the cost of water but what are your environmental conditions. Can you get enough cooling and keep the Relative Humidity in range to not cause issues? Even if you have balanced airflow all of the water you put into the air is not getting outside through the exit fan. A portion of it will go into the building materials somewhere due to air pressure differences between the inside and outside. When conditions are right you will then have a place for mold and rot to occur. If the evaporative cooling takes the RH from say 30% to 50% then the portion that goes into the building materials likely won't build up enough moisture in the materials to support mold, mildew, or fungus growth. But I have a feeling doing much evaporative cooling isn't a great idea in your climate.

I think you would be best to understand how your apartment is heating up. Since you state it gets hot quickly then takes a long while to cool down, I don't think all of it is due to solar gain through the walls, as in the sun shining on the walls outside and warming up the thermal mass which then releases the heat inside. I think the majority of it is heat gain through windows (solar gain) as well as air leakage. So you are in effect heating the thermal mass from the inside and the outside. The kicker of it is that likely the majority of the through the window solar gain isn't happening in your apartment, but in those below you. BSI-075: How Do Buildings Stack Up? | Building Science Corporation

You would likely do best to understand how your apartment is heating up. Get your air leakage measured, measure the internal temperature and the outside ambient temperature, measure the temperature of the walls, floor, and ceiling in many places, measure your pressure differences. From that data a theory on how best to implement energy efficient cooling strategies can be developed and then tested.

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